Digitally injected designs in powder surfaces

Abstract

Building panels and a method to produce such panels including a solid decorative surface having a decorative wear layer including fibres, binders, colour substance, wear resistant particles and a digital ink print.

Claims

1. A method for producing a decorative surface layer, comprising the steps of: applying a first powder, in powder form, on a substrate to form a first powder layer; printing a first print with first ink drops on the first powder layer; spraying a first colored liquid substance on the first powder layer; applying a second powder, in powder form, on the first powder layer to form a second powder layer after the printing of the first print and the spraying of the first colored liquid substance on the first powder layer; printing a second print with second ink drops on the second powder layer; spraying a second colored liquid substance on the second powder layer; and pressing the first and second powder layers to form the decorative surface layer, wherein the printing of the first and second prints is performed by controlling a printed position of each ink drop, and the spraying of the first colored substance is performed by randomly distributing the first colored substance over a first sprayed area and the spraying of the second colored substance is performed by randomly distributing the second colored substance over a second sprayed area, wherein at least some of the second ink drops positioned over at least some of the first ink drops are in direct contact with the at least some of the first ink drops.

2. The method as claimed in claim 1, wherein the ink drops of the first print are positioned in the surface layer at different vertical depths.

3. The method as claimed in claim 2, wherein the average size of the ink drops at an upper vertical position is smaller than the average size of the ink drops at a lower vertical position.

4. The method as claimed in claim 1, wherein the average size of the ink drops in the second powder layer is smaller than the average size of the ink drops in the first layer.

5. The method as claimed in claim 1, wherein the ink drops are of variable size and/or variable colour.

6. The method as claimed in claim 1, wherein the second powder comprises bleached wood fibres and wear resistant particles with a thermosetting binder.

7. The method as claimed in claim 1, wherein the second powder comprises a thermoplastic material and wear resistant particles.

8. The method as claimed in claim 1, wherein the second powder is a semi-transparent powder.

9. The method as claimed in claim 1, wherein the first powder includes fibres and a binder.

10. The method as claimed in claim 9, wherein the fibres are wood fibres.

11. The method as claimed in claim 10, wherein the wood fibres are bleached.

12. The method as claimed in claim 9, wherein the binder is a thermosetting binder.

13. The method as claimed in claim 9, wherein the binder is a thermoplastic binder.

14. The method as claimed in claim 1, wherein the first powder includes a colour substance.

15. The method as claimed in claim 1, wherein the first powder includes wear resistant particles.

16. The method as claimed in claim 1, wherein the second powder includes fibres and a binder.

17. The method as claimed in claim 16, wherein the fibres are wood fibres.

18. The method as claimed in claim 16, wherein the wood fibres are bleached.

19. The method as claimed in claim 16, wherein the binder is a thermosetting binder.

20. The method as claimed in claim 16, wherein the binder is a thermoplastic binder.

21. The method as claimed in claim 1, wherein the second powder includes a colour substance.

22. The method as claimed in claim 1, wherein the second powder includes wear resistant particles.

23. The method as claimed in claim 1, wherein the first powder is a plastic powder.

24. The method as claimed in claim 1, wherein the second powder is a plastic powder.

25. The method as claimed in claim 1, wherein the first printing is made by digital printing.

26. A method for producing a decorative surface layer, comprising the steps of: applying a first powder, in powder form, on a substrate to form a first powder layer, the first powder comprising first color pigments; printing a first print with first ink drops on the first powder layer; spraying a first colored liquid substance on the first powder layer; applying a second powder, in powder form, on the first powder layer to form a second powder layer after the printing of the first print and the spraying of the first colored liquid substance on the first powder layer, the second powder comprising second color pigments; printing a second print with second ink drops on the second powder layer; spraying a second colored liquid substance on the second powder layer; and pressing the first and second powder layers to form the decorative surface layer, wherein the printing of the first and second prints is performed by controlling a printed position of each of the first and second ink drops, and the spraying of the first colored substance is performed by randomly distributing the first colored substance over a first sprayed area and the spraying of the second colored substance is performed by randomly distributing the second colored substance over a second sprayed area, wherein at least some of the second ink drops positioned over at least some of the first ink drops are in direct contact with the at least some of the first ink drops.

27. The method as claimed in claim 1, wherein the second printing is made by digital printing.

28. The method as claimed in claim 1, wherein the first and the second ink drops are of variable size.

29. A method for producing a decorative surface layer, comprising the steps of: applying a first powder, in powder form, on a substrate to form a first powder layer; printing a first print with first ink drops on the first powder layer; applying a second powder, in powder form, on the first powder layer to form a second powder layer; printing a second print with second ink drops on the second powder layer, the second ink drops being larger than the first ink drops printed on the first powder layer; and applying heat and pressure on the first and second powder layers on the substrate to cure the first and second powder layers into the decorative surface layer which possesses the first print and the second print, wherein at least some of the second ink drops positioned over at least some of the first ink drops are in direct contact with the at least some of the first ink drops.

30. The method as claimed in claim 29, wherein the first ink drops are each less than 5 picoliters in size, and the second ink drops are each between 5-20 picoliters in size.

31. A method for producing a decorative surface layer, comprising the steps of: applying a first powder, in powder form, on a substrate to form a first powder layer; printing a first print with first ink drops on the first powder layer, wherein the first ink drops are of variable size; spraying a first colored liquid substance on the first powder layer; applying a second powder, in powder form, on the first powder layer to form a second powder layer after the printing of the first print and the spraying of the first colored liquid substance on the first powder layer; printing a second print with second ink drops on the second powder layer; spraying a second colored liquid substance on the second powder layer, the second colored liquid substance being a different color than the first colored liquid substance; and pressing the first and second powder layers to form the decorative surface layer, wherein at least some of the second ink drops positioned over at least some of the first ink drops are in direct contact with the at least some of the first ink drops.

32. The method as claimed in claim 25, wherein the second printing is made by digital printing.

33. The method as claimed in claim 26, wherein the first and second color pigments in the first and second powder layers are different colors from one another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will in the following be described in connection to preferred embodiments and in greater detail with reference to the appended exemplary drawings, wherein,

(2) FIGS. 1a-b Illustrate a known WFF panel and a know digital printing method;

(3) FIGS. 2a-b Illustrate a method to form a decorative surface with a deep print;

(4) FIGS. 3a-e Illustrate panels having a decorative surface with a digital print;

(5) FIGS. 4a-b Illustrate panels having a decorative surface with a high definition print that extends deep into the surface;

(6) FIGS. 5a-e Illustrate a method to make a decorative surface with a combination of a base colour, a print and a liquid colour substance;

(7) FIGS. 6a-d Illustrate methods to form a decorative surface;

(8) FIGS. 7a-b Illustrate alternative methods to form a decorative surface;

(9) FIGS. 8a-h Illustrate methods to test wear resistance and print depth of a printed decorative surface;

(10) FIG. 9 Illustrate a decorative surface produced by a combination of a base colour, printing and a liquid colour substance.

(11) FIGS. 10a-c Illustrate a decorative surface with in register embossing and with a printed pattern that varies.

(12) FIGS. 11a-d Illustrate a decorative surface comprising two powder layers and a print

(13) FIGS. 12a-e Illustrate a decorative surface with in register embossing and with a printed pattern that varies.

(14) FIGS. 13a-e Illustrate a decorative surface and a print with drop size that varies between two layers

(15) FIGS. 14a-d Illustrate a production method to change the position of embossed portions in a panel surface.

(16) FIGS. 15a-e Illustrate a production method to form panels that can create a synchronized large pattern

(17) FIGS. 16a-d Illustrate examples of the embodiments of the invention.

(18) FIGS. 17a-e Illustrate examples of the embodiments of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(19) FIG. 1a shows the upper part of a known Wood Fibre FloorWFFas described in WO 2009/065769 (Applicant Vlinge Innovation) with a solid decorative surface 5 comprising a mixture of fibres, preferably wood fibres 14, small hard wear resistant particles 12, 12, preferably aluminium oxide, and a binder 19, preferably thermosetting resin such as for example a melamine formaldehyde resin. A wide variety of designs can be obtained by mixing colour substances such, as for example, colour pigments with fibres, binders and aluminium oxide particles in dry form and by applying the WFF mix as powder on a core that is cured in a press under heat and pressure. Such a mix of materials comprising fibres, preferably wood fibres, binders, wear resistant particles and an optional colour substance that is applied as powder on a carrier is hereafter referred to as a WFF mix. A mix that only comprises wood fibres and binder in powder form is hereafter referred to as a Wood powder mix such a mix can be used in applications where a high wear resistance is not needed for example in wall panels or furniture components.

(20) FIG. 1b shows a known digital printing method, which is described in WO 2009065769. A digital ink jet printing head 24 can be used to print a pattern on and into the powder before pressing such that the ink 32 penetrates about 0.1-1 mm into the powder.

(21) Such a method may for example be used to print grout lines and to create a tile pattern. The ink can penetrate deep into the powder and a printed pattern with a high wear resistance can be obtained. Rough wood grain structures can also be formed.

(22) A deep print can be provided in several ways.

(23) Ink may be used that penetrates into the fibres and that flows around and between the fibres. A deep penetration of for example 0.1-0.5 mm can be obtained if a sufficient amount of ink is applied on the powder. Such deep penetration can give a very high wear resistance. High quality laminate floorings have a wear resistance of 4000-6000 revolutions, which corresponds to the abrasion classes AC4 and AC5 measured with a Taber Abraser according to ISO-standard.

(24) A deep print in a powder based surface can be made that can obtain a wear resistance of 30,000 to 50,000 revolutions.

(25) FIG. 2 a shows that ink can also be applied by an ink head 24 with pressure that removes the powder based WFF mix 5 and forms a V or U formed groove 4. The walls and the inner lower parts 32 of the groove are coloured by the ink. A deep print 10 is obtained after pressing as shown in FIG. 2b. The ink head 24 is shown schematically.

(26) A high definition digital printer with a resolution of for example 300 DPI sprays about 12 ink dots per mm that are about 0.05 mm wide.

(27) FIG. 3a shows that a digital ink-printing device may be used to create a high definition print 10a, 10b in a WFF mix 5 or a wood powder mix that does not comprise any wear resistant particles. FIG. 3b shows that the ink can be applied as a print 10b on all parts that are included in the mix. Fibres 14, preferably aluminium oxide particles 12 and melamine particles 19 are printed. The mix preferably also comprises a colour substance 15 (not shown) that provides a base colour. Such print can be made with the same quality as printing on paper especially if the drop size and the drop volume of the ink are adapted to the mix structure and the size of the fibres. The drop volume is measured in picoliters ( 1/1,000,000,000,000 of a litre) and can vary from for example 1 to 50 picoliters. The quality can be increased further if the powder for example is pre pressed before printing such that the fibres are not displaced horizontally during the final pressing and/or if small wood fibres with for example a width of less than 0.05 mm and length of less than 0.5 mm are used. The ink content can be rather low and the ink can be applied in a way that it is not floating along the fibres and between the fibre layers. The ink is during pressing mixed with the binders and partly pressed to the fibres. Such high definition print with a printing quality of 100 DPI and more can be obtained with a depth D that preferably is equal to the thickness of the fibres. The depth D of the print is about the same in prints 10a that have a considerable width W1 of for example 1 mm and more as in prints 10b that are similar to thin lines with a width of for example 0.1 mm.

(28) The wear resistance of a high definition print applied on a powder based WFF mix as described above and with a depth D of 0.03-0.05 mm can be about 2,000-3,000 revolutions provided that the mix comprises a sufficient content of wear resistant particles, for example 10-20% (weight) aluminium oxide particles. This exceeds AC 3 (>2,000 revolutions) and is sufficient for domestic applications.

(29) Several methods can be used to increase the wear resistance further.

(30) A transparent wear layer 7 can be applied over the print 10a, 10b as shown in FIG. 3c. Such wear layer can preferably comprise wear resistant particles preferably transparent aluminium oxide particles or a binder for example melamine or a mix of for example melamine powder and aluminium oxide particles that can be pressed into and on the print. This method can be used to increase the depth of the print and/or to increase the content of the wear resistant particles in the upper part of the surface. Even transparent or semi transparent alpha cellulose fibres can be included in the mix that can be applied as a dry powder layer or in liquid form. Conventional overlay used in conventional laminate flooring can also be used.

(31) FIG. 3d shows that the print 10a, 10b can be coordinated with an embossed surface. Such coordinated embossing can be very accurate and the tolerance between the print 10a and the embossed portions 9 can be much better than in conventional laminate where the printed paper swells during impregnation in an uncontrolled way and where the positioning of the paper increases the tolerances further. Coordinated embossing or embossing in register in powder based surfaces as described above can be made with a tolerance that is less than 1.0 mm. A long and short edge of the board can be used as reference during printing and pressing. Printed positioning spots or lines can also be used. The print can be positioned very precisely in the lower parts of the embossed surface portion 9. The upper parts of the surface 8 will protect the print 10a, 10b from wear. The width EW of the embossed portion 9 can be made larger then than width W of the print 10a in order to eliminate production tolerances and to assure that the printed pattern is protected by surface portions, which are located above the print. The depth DE of the embossed portion can be about 0.05-0.10 mm and this is generally sufficient to increase the wear with for example 2000-4000 revolutions. A WFF mix allows that very deep embossing with an embossing depth DE of for example 0.10-1.0 mm can be formed and this can be used to produce floor panels with a very high wear resistance.

(32) FIG. 3e shows that all the described methods can be combined. A transparent wear layer can for example be provided over the embossed parts 9 with the print 10a, 10b located in the lower part of the embossing.

(33) The ink content can be much lower than in other conventional digital printed surfaces where ink is applied on a paper. The powder in the WFF mix can be coloured with a base colour or several colours that are mixed together. A powder layer with one colour can be applied in patterns on another powder layer having a different colour. Such colours or combination of colours can for example provide the base colour or base pattern of a wood design. Only a very limited amount of ink is needed to for example create a wood grain structure on the base pattern or colour. The ink can cover less than 50% of the design. In some applications less than 30% or even less than 10% can be sufficient to obtain a wood design. Additional decorative substances can be sprayed over the base colour prior and/or after the printing step. Very advanced designs can be created with a combination of one of several powder layers comprising one or several base colours, digital ink jet printing and spraying of one or several colour substances.

(34) FIG. 4a shows that a high definition print 10a can be combined with a high wear resistance. The first print 16 is provided on a first powder layer L1. A second powder layer L2 is applied on the first layer L1 and a second print 17 is provided on the second powder layer. The prints are positioned over each other such that parts of the two prints are preferably connected vertically. The wear resistance can be increased considerably and a high definition print with a wear resistance of for example 6,000 revolutions equal to AC 5 can be obtained. Such surface quality can be used in commercial applications. The surface layer 5 comprises a first horizontal plane H1 and a second horizontal plane H2 under the first horizontal plane H1 and a vertical plane VP perpendicular to the horizontal planes. The colour content of the print 10 is in this embodiment higher in a second horizontal plane H2 than in a first horizontal plane H1 located over the second horizontal plane. It is preferred that such variation of the colour content varies along the vertical plane VP. This means that the prints 16, 17 are positioned above each other and that the pattern will be substantially the same when the surface is subjected to wear. The prints 10b, 10c can also be made with a first 16 and a second 17 print that are offset but in contact or completely offset without contact along the vertical plane. The printed pattern will vary when the surface is subjected to wear. The two prints can have different designs. The colour and/or the pattern can for example be different in the first layer compared to the second layer.

(35) The second layer L2 comprises preferably a WFF mix of 50-100 gram/m2.

(36) FIG. 4b shows that three prints provided on three layers can be used to reach a high definition print with a wear resistance of 9,000 revolutions similar to AC 6 (>8,500 revolutions).

(37) It is for example possible to apply 4-10 layers and prints and this makes it possible to create a surface with the same structure as a solid wood veneer where the wood grains designs extend from the top to the bottom of the surface layer. The wear resistance can be extremely high and 20,000-30,000 revolutions can be reached.

(38) Digital prints in one or several layers can be applied on a mix comprising different material compositions. All materials described above can be combined or used separately. A first and/or a second layer can for example comprise a mix of: Only plastic particles; Plastic particles with a colour substance; Plastic particles with wear resistant particles; Only fibres; Only binders; Only wear resistant particles; Only a colour substance; Fibres and a binder; Fibres and a colour substance; Fibres, binders and wear resistant particles; Fibres, binders and a colour substance; or Fibres, binders, colour substance and wear resistant particles.

(39) Other materials such as fibres and/or colour substance and/or wear resistant particles and/or binders can be added after a first and/or a second print etc.

(40) The binders in one layer can be used to cure a second layer since the binders will during pressing float between different layers.

(41) The principles described above can be used to produce a panel where the powder and a print are applied on a core material. The principles can also be used to produce separate surface layers that can be glued to a core.

(42) The principles can also be used in combination with other printing methods.

(43) Digital ink printing can in all embodiments as described above be combined or replaced by other printing methods such as transfer printing, stamp printing and similar know methods.

(44) Some or all of the layers L1, L2 and L3 can comprise transparent or semi transparent fibres preferably processed and bleached wood fibres. This can be used to create 3D effect as described in other sections below.

(45) Wood fibres and transparent or semi transparent alpha cellulose fibres can in all embodiments of this invention be replaced by thermo plastic powder, preferably vinyl powder. A binder is in such an embodiment not needed. It is preferred that such plastic particles have a diameter of about less than 0.3 mm, even more preferably about less than 0.1 mm. A digital print can be applied in one or several layers preferably comprising a transparent plastic mix of vinyl powder and preferably also wear resistant particles for example aluminium oxide particles. The plastic layers are exposed to heat and preferably also pressure. The surface is thereafter cooled and a perfect 3D design can be obtained with perfect visibility between the different transparent layers. A flexible plastic surface can be obtained with ink particles embedded into a plastic layer and such a surface layer can be combined with all types of core materials, preferably mineral based board materials, plastic boards or board material for exterior application that are not sensitive to moisture variations. Swelling and shrinking of the board and the surface in different humidity conditions can be avoided. It is preferred that the board surface is not visible. This can be obtained in several ways. The board can be coloured or coated with an impregnated paper. A plastic coloured sub layer can also be used as a base for the transparent layers. The plastic layers can also be mixed with wood fibres, preferably bleached semi transparent alpha cellulose fibres.

(46) FIGS. 5a-5e show how a surface design can be formed that comprises a high definition print 10 that has a high wear resistance. A WFF mix 5a is applied on a carrier, for example a HDF core 6 as shown in FIG. 5b as a base layer. The mix comprises a base colour 15. A first digital ink print 16 is preferably applied on the base layer as shown in FIG. 5c. The ink can be water or solvent based. A liquid colour substance 30 is preferably sprayed on the first print and the base colour. Spraying can be used to coat the mix with small drops that are not individually controlled as in digital printing. Spraying can be used to create specific patterns with small drops that are applied at random within specific surface portions. A new WFF mix 5b is applied as a second layer on the first print 16. The second layer can have the same composition as the first layer. It can also have a different composition. The amount or size of the aluminium particles and/or binders can be different. The second layer has preferably a higher content of binders and/or wear resistant particles than the first layer. The thickness of the second layer is preferably 0.01-0.1 mm. This corresponds to about 10-150-gram/m2. A second print 17 is preferably applied on the second layer 5b as shown in FIG. 5e and a second liquid colour substance 30, is preferably sprayed over the second print.

(47) Spraying of colour substances on one or several layers of a WFF mix can be made without printing in order to improve the decorative properties of the decorative surface layer 5. Wear resistant particles can be excluded if for example the intension is to produce panels for vertical or decorative applications.

(48) FIG. 6a shows schematically a production line for production of a building panel comprising a decorative surface 5 connected to a core 6. A conveyor belt 23 moves the board 6 such that it passes several scattering station 20a, 20b. A scattering device 20a applies a WFF mix or a wood powder mix as a dry powder on a carrier 6 that preferably is sheet material, for example a HDF board. The mix is preferably pre pressed and the pre-pressing device is in this embodiment preferably a roller 29. Alternatively a discontinuous or continuous pressing device can be used. A balancing layer of for example impregnated paper or a powder layer is preferably applied prior to this first scattering provided on the rear side of the core 6.

(49) A particular problem with pre pressing is that WFF powder will stick to the pressure surface 26 of the pre-pressing device 29 that is in contact with the powder. The fibres of the pre pressed surface will not form an even base for the print. This problem can be solved if the pressure surface 26 is a high gloss steal roller, band or plate. Sticking problems can be reduced or avoided with very high gloss pressure surfaces 26. A mix with low moisture content, preferably less than 6%, is also favourable in order to eliminate sticking problems.

(50) A decorative pattern is provided on the WFF mix by a digital ink printing device 21. The print 10b is applied on the fibres 14 and all other parts included in the mix as shown in FIG. 6b.

(51) Preferably a second scattering station 20b applies transparent aluminium oxide particles 12 and/or melamine powder 19 over the print 10b. A stabilizing unit 22 sprays a liquid substance preferably a water solution comprising de-ionized water over the WFF mix and the print 10b. This spaying prevents the powder to be displaced and to blow away during the final pressing operation. The stabilizing unit 22 can also comprise several spray heads that can apply one or several liquid colour substances 30 on the surface 5 in order to improve the decorative effects. A heating device 24 can be used to remove water from the colour or the water based stabilizing substance that is applied prior to pressing. The heating is preferably made with infra red lights. The core 6 and the printed surface 5 are finally pressed in a press 25 under heat and pressure such that the WFF powder and the print cures to a hard and wear resistant decorative surface layer.

(52) FIG. 6d shows a similar production line. The difference compared to FIG. 6a is that there are two digital ink printing devices or printers 21, 21. The first digital ink-printing device applies a print on a first layer of a WFF mix in the same way as in FIG. 6a. A second scattering unit 20b applies a second layer of a WFF mix over the first print and the second digital ink printing device 21 applied a second print over the second WFF layer. A liquid substance is sprayed over the surface by the stabilizing unit 22 and the panel is finally pressed in a press 25. Printing is in this embodiment applied on a scattered surface without pre pressing. It is obvious that the two production methods shown in FIGS. 6a and 6d can be combined. One or several pre pressing steps can for example be provided prior to the printing as shown in FIG. 7a and a third or fourth scattering unit (not shown) can for example apply aluminium oxide and/or binders over the first and/or second print. A liquid colour substance can also be provided prior or after the first and/or the second print.

(53) FIG. 7b shows that one scattering unit 20 and one digital ink-printing device 21 can be used to apply and print several WFF layers. The conveyor is reversed after the first print and a second WFF layer can be applied and printed. The advantage is that the position of the board can be controlled very accurately and the prints can be positioned precisely over each other. These steps can be repeated and many layers and prints can be applied. Several alternative movements of the panel can be made. The panel can for example be displaced horizontally and perpendicularly to the feeding direction and than moved backwards by a second conveyor to the original starting position.

(54) FIGS. 8a-8c shows how that colour intensity 10a-10c decreases in a multi printed WFF layer when the surface is subject to wear according to the above-described Taber Abraser testing method. FIG. 8a shows the original surface and FIGS. 8b and 8c show the surface after, for example, 1000-2000 revolutions depending on the print quality. FIG. 8d shows that the colour intensity increases again after for example 3000 revolutions due to the fact that the first printed layer becomes visible. FIGS. 8e-8h shows a single print in a WFF layer. The colour intensity 10a-10d decreases continuously when the surface is subject to wear.

(55) FIG. 9 shows a surface layer 5 according to an embodiment of the invention with a decorative pattern that is a copy of a wood veneer. The decorative surface comprises a base colour 15, a digital ink print 10 and a liquid colour substance 30.

(56) Embossing is preferably made when the powder mix is pressed against an embossed metal plate a matrix. In continuous presses an embossed metal belt or a matrix paper is used. The embossing structure is identical for all pressed boards and this gives a repetition effect. Such problems can be avoided if for example the print 10a, 10b varies between pressing steps as shown in FIGS. 10a-10c. FIG. 10 b shows an embossed portion 9b that has no print. FIG. 10c show embossed portions 9a and 9b that have a different print 10c, 10d than the print in 10a and 10b in FIG. 10a. The colour or the size of the print varies between the same embossed portions in different panels. Such a variable in register embossing will create a visual pattern that looks different in spite of the fact that embossing is identical. This is further shown in FIGS. 12a-12e. A first powder layer L1 and a first print 10a, 10b is applied on a board (FIG. 12b) and the board is pressed against an embossed press plate such that embossed portions 9a, 9b are formed in register with the print 10, 10b as shown in FIGS. 12a-12c. FIGS. 12d and 12e show that the print can be changed between pressing operations. The print 10c, 10d as shown in FIG. 12d can be slightly different than a second print 10e, 10b in a second pressing as shown in FIG. 12e. Colours and shapes can be varied and visible repletion effects can be eliminated.

(57) Repetition effects related to embossed structures can be further reduced if for example the press pate 40 is equipped with a sliding device as, shown in FIGS. 14a-14d, that allows the press plate 40 with its embossed portions 9a, 9b, 9c and 9d to be displaced between the pressing steps and the position of the embossed structure on the floor panels can vary. The sliding device can be combined with a heating plate 39 that heats the parts of the press plate that are displaced outside the press table 41. Such a sliding press plate embossing requires that the position of the printed patter 10a, 10b as shown in FIG. 14a can also be adjusted. Digital printing allows that a different print 10a, 10b, 10c is applied on the board 2 as shown in FIG. 14b. As an alternative an embossed press plate that is larger than the pressed board 2 can be used and the position of the board can vary between different pressing steps as shown in FIGS. 14c, 14d. This can be made in a simple way with digital printing and the printed pattern 10 can be adjusted such that it always is coordinate with the position of the press plate or the board.

(58) All these principle can be combined and a vide range of individual panels with in register embossing but without visible repetition effects can be obtain. This method can be used in conventional laminate floors. The digital print is in such embodiments applied in the conventional way on the board or on a paper layer.

(59) FIGS. 11a-11d show how several powder layers and a digital print can be combined to provide an advanced and cost effective printed pattern. A first powder layer L1 is applied on a board 6 as shown in FIG. 11b. The first powder layer L1 comprises a first base colour. A second powder layer L2 with a second base colour is applied on a part of the surface with by scattering through a template. A digital print is applied on the first and/or second layers. The advantage is that an advanced pattern can be created with limited ink and this can increase the printing speed.

(60) FIGS. 13a-13d show that different drop sizes can be used, preferably in different semi transparent layers, in order to create an advanced 3D pattern. A first transparent or semi transparent powder layer L1 is applied on a core 6 that can have a virgin colour or that can be coloured in the conventional way of by a powder layer that has been applied on the core and that comprises a base colour. A digital print injects ink drops 11a, 11b into the first powder layer L1 as shown in FIG. 13b. A second transparent or semi transparent powder layer L2 is applied on the first powder layer L1 and a second digital print injects ink drops 11c, 11d into the second and upper top layer L2. The ink drops in the second layer can be smaller and this gives a high definition print. Drops that are position vertically over each other along a vertical plane VP can create the visible pattern. Such drops can have different size and colour. The design will look different if it is looked upon vertically in the D1 direction or from an angle in the D2 direction as shown in FIG. 13e and this will create an advance design that is not possible to obtain when a print is provided by placing drops on a layer side by side.

(61) FIGS. 15a 15e show how a large pattern can be formed that comprises several building panels 1,1. The problems related to the positioning and forming of a locking system and the adjustment of the design due to material waste of surface material can be eliminated. A locking system 3a, 3b is machined in a core material 6 for example HDF as shown in FIG. 15a and the panels 1, 1 are connected to a large board. A powder mix, preferably a WFF mix, is applied on the connected panels and the mix is printed with a print 10a, 10b as shown in FIGS. 15b, 15c. The board comprising several panels is pressed and the surface is cured. The surface will crack along the joint 4a, 4b when the panels are released from each other as shown in FIG. 15e. Surprisingly a powder based surface will crack along a very straight line and the panels can be used and connected without any further machining of the edges 4a,4b. However, some further machining can be made in order to for example polish the edges or to make small bevels. This limited machining will generally not have any effect on the large pattern, that in spite of the fact that it comprises several panels, will look as one single large pattern or picture that can cover a large area of a floor or a wall.

(62) Where the term Powder Layer is used as a term for a pressed board it is meant a layer that was distributed as powder prior to pressing.

EXAMPLES

(63) The terms used in the examples below are defined as follows:

(64) Base color powder layer is a powder layer with a specific color that aims to be fully or partly visual in the final product. The color is typically created by mixing pigment to the powder. A base color powder layer can cover parts of or the full surface.

(65) Semicolored transparent layer is a WFF layer which comprises one part of base color powder and 5-20 parts of semitransparent like the exemplary recipe below. This mixture is used to keep the color at the same color gamut as the base color powder layer.

(66) Semitransparent layera WFF layer that is transparent or semitransparent after pressing. This layer is adapted to be suitable to print in. A typical composition of such a layer is: 1 part alpha cellulose, 0.5-1 part aluminium oxide, 1-1.5 part melamine. A layer of for example 100 gram/m2 is quite transparent but a layer of 600 grams/m2 is very milky.

Example 1

(67) On a HDF board with a thickness of 9.8 mm, two backing papers NKR 140 where fixed on backside for balancing, a WFF powder formulation was added, comprising of 24.5% wood fibre, 17.5% aluminium oxide, 10.5% titanium dioxide as pigment and 47.5% melamine resin.

(68) The WFF powder mix was applied as a first layer by a so-called scattering machine, which distributed the WFF powder material evenly over the HDF surface. The totally amount of WFF powder was 400 g/m.sup.2.

(69) A print was applied on the powder by a digital printing device and with a printing quality of 300 DPI.

(70) A second layer with the same composition as the first layer and with an amount of about 100 g/m2 was applied over the first layer and over the print.

(71) A second print was applied on the second layer as a matching pattern located over the first print.

(72) The WFF powder was fixed on the HDF board by spraying a water solution comprising of 97% de-ionize water, 1% BYK-345 (reducing surface tension) and 2% of Pat 622/E (release agent) on the WFF powder.

(73) The above material was placed into a so-called DPL press and pressed at 40 bar in 25 sec with a temperature on the upper daylight at 160 C. and the bottom daylight at 165 C.

(74) A powder based solid surface with a high definition print and with a wear resistance exceeding 6,000 revolutions according to the abrasion class AC5 measured with a Taber Abraser according to ISO-standard was obtained.

Example 2

(75) Example 1 was repeated with the first WFF powder layer pre pressed prior to the first printing and the second WFF layer pre pressed prior to the second printing.

(76) A powder based solid surface with a high definition print and with a wear resistance exceeding 6,000 revolutions according to the abrasion class AC5 measured with a Taber Abraser according to ISO-standard was obtained. The printed pattern in example 2 was more distinct then the pattern in example 1.

(77) All examples below are described from top surface and then down trough the structure.

Example 3

(78) FIG. 16a

(79) Print 17 (part or full print, spot or cmyk-print)

(80) Base color powder layer L2 or Semicolored transparent layer, 41-208 g/m2 preferably 125 g/m2.

(81) Print 16 (part or full print, spot or cmyk-print)

(82) Base color powder layer L1 125 g/m2-833 g/m2, preferably 500 g/m2.

(83) Core 6

(84) Backing/balancing layer 27

(85) By adapting the ratio between the powder layers an acceptable wear picture can be achieved until the lower layer of print is worn down.

Example 4

(86) FIG. 16a

(87) Print 17 (part or full print, spot or cmyk-print)

(88) Transparent powder layer consisting of thermoplastic particles and wear resistant particles L2 or Semicolored transparent layer consisting of thermoplastic particles, wear resistant particles and pigments, 30-500 g/m2 preferably 100-300 g/m2. Also alpha-cellulose particles can be incorporated into the transparent or Semicolored transparent layer.

(89) Print 16 (part or full print, spot or cmyk-print)

(90) Base color powder layer L1 125 g/m2-833 g/m2, preferably 500 g/m2.

(91) Core 6

(92) Backing/balancing layer 27

(93) By adapting the ration between the powder layers an acceptable wear picture can be achieved until the lower layer of print is worn down.

Example 5

(94) FIG. 16b

(95) Spot color ink, part print 10

(96) Base color powder layer 125 g/m2-800 g/m2, preferably 625 g/m2 L2

(97) Core 6

(98) Backing/balancing layer 27

(99) Simple and low cost printer configuration due to only one color to print. Low ink consumption since parts of the visual color is created by the powder.

Example 6

(100) FIG. 16c

(101) Spot color ink, part print 10

(102) Base color powder layer 5 or Semicolored transparent layer, partly covering the surface (scattered with or without coordination with the print) 40 g/m2-125 g/m2, preferably 125 g/m2

(103) Base color powder layer 5a,5b (differs in color compared to the other base color layer) 125 g/m2-800 g/m2, preferably 625 g/m2

(104) Core 6

(105) Backing/balancing layer 27

(106) Comment type 2Same as type 1 but more advanced design possible since two or several powder colors and one print color are visual in the final in the final product.

Example 7

(107) FIG. 16d

(108) CMYK part print 10

(109) Base color powder layer L1, 125 g/m2-800 g/m2, preferably 625 g/m2.

(110) Core 6

(111) Backing/balancing layer 27

(112) Comment type 3same as type 1 but a standard cmyk configured printer concept can be used.

Example 8

(113) FIG. 17a

(114) CMYK full print 10

(115) Semitransparent layer or Semicolored transparent layer L1, 125 g/m2-800 g/m2, preferably 625 g/m2.

(116) Core 6, backing 27

(117) Comment type 4due to the semitransparent layer a 3 dimensional visual effect can be achieved that enhances the product appearance. Very good wear resistance properties can be reached corresponding to AC3 according to standard EN13329:2006+A1:2008.

Example 9

(118) FIG. 17b

(119) CMYK full print 17

(120) Semitransparent or Semicolored transparent layer L2 (for example, 150 gram/m2)

(121) CMYK full print 16

(122) Semitransparent or Semicolored transparent layer L2 (typically thicker than the upper layerfor example 400 gram/m2)

(123) Core 6

(124) Backing/balancing layer 27

(125) Comment type 5better wear resistance than type 4 due to double print and scattering generating a real 3 dimensional print in the wear layer.

Example 10

(126) FIG. 17c

(127) Print 17 (cmyk or spot-color, part or full print)

(128) Semitransparent layer L2, 40 g/m2-300 g/m2, preferably 125 g/m2.

(129) Print 16 (cmyk or spot-color, part or full print)

(130) Base color powder layer L1, 125 g/m2-800 g/m2, preferably 500 g/m2.

(131) Core 6

(132) Backing/balancing layer 27

(133) Comment to example 10good wear resistance due to double print layer and scattering. The base color of the lower powder layer covers the substrate color and functions as one of the visual colors when the printed layers only is part printed. Very good wear resistance properties can be reached, over AC6 according to standard EN 13329:2006+A1:2008.

(134) The product can be tailor made to meet the requirements of most wear situations by additional powder and print layers.

(135) This embodiment has been produced in three different modes regarding print layer thickness.

(136) Print (cmyk or spot-color, part or full print)

(137) Semitransparent layer, called STL in description below.

(138) Print (cmyk or spot-color, part or full print)

(139) Base color powder layer, called BPL in description below.

(140) Core

(141) Balancing layer/backing

(142) TABLE-US-00002 Type BPL STL Abrasion(REV) Comment TYPE 375 g/m2 250 g/m2 >19,000 A 9a TYPE 458 g/m2 166 g/m2 15,000 B 9b TYPE 541 g/m2 83 g/m2 7,000 C 9c Comments: A. Very durable but a bit of haze appears due to thick semitransparent print layers. The printed pattern is still intact after 19,000 revolutions. B. Best mode, nice crisp colors in print all through the abrasion process. C. Nice crisp colors all through abrasion process but not so good in abrasion properties due to very thin semitransparent print layer.

Example 11

(143) FIG. 17d

(144) Print 17 (cmyk or spot-color, part or full print)

(145) Transparent or semitransparent layer L2 made of thermoplastic particles and aluminium oxide particles, 40 g/m2-300 g/m2, preferably 125 g/m2.

(146) Print 16 (cmyk or spot-color, part or full print)

(147) Base color powder layer consisting of refined fibres and thermoplastic particles L1, 125 g/m2-5000 g/m2, preferably 200-1000 g/m2 if the produced layer should be glued to another core or 1000-5000 g/m2 if the material it self should be machined with mechanical locking systems for floating installation. For thicker panels even more material can be used.

Example 12

(148) FIG. 17e

(149) Print 17 (cmyk or spot-color, part or full print)

(150) Transparent or semitransparent layer L2 made of thermoplastic particles and aluminium oxide particles, 40 g/m2-300 g/m2, preferably 125 g/m2.

(151) Base color powder layer consisting of refined fibres and thermoplastic particles L1, 125 g/m2-5000 g/m2, preferably 200-1000 g/m2 if the produced layer should be glued to another core or 1000-5000 g/m2 if the material it self should be machined with mechanical locking systems for floating installation. For thicker panels even more material can be used.

Example 13

(152) All described samples mentioned so far in this text have been made with a scanning Epson print head shooting 3.5 pl drops at a resolution corresponding to 720720.

(153) Wear resistant particles can in all examples above be excluded if the intention is to produce a panel for vertical application where a high wear resistance is not needed.

(154) Binders and preferably also fibres in all examples above can be excluded if thermoplastic powder particles are used that melts together when exposed to heat.